Best thing to do with slime is put it in the bin, but that's just my opinion.
+1. Just carry a spare tube or tub, and learn how to change it. Any fillers add weight (not a lot, bit some) to rotating weight, and if you do get a puncture it's better to know, before it goes again and catches you out. It does of course settle at the bottom of a wheel when stationary, and feels very odd for the first few rotations. There is a similar product for motos - where a puncture is a much messier business and tyres are tubeless anyway - which works simply because they are tubeless. Anything with a tube in that punctures has two holes, one in the outer and one in the tube, and the item that caused the penetrations needs to be removed, so quite how slime or any other product can help that I fail to see.
Fans will say it just works, fine if they are happy with that. I like to know what the real situation is.